This invention relates to a cassette holder for positioning an X-ray film cassette in the path of an incoming X-ray beam.
In X-ray processes such as the taking of chest X-rays, the generated X-rays are formed into a beam by a collimator which directs the beam toward the chest of the patient and onto sensitive X-ray film that is contained in a rectangular cassette positioned beyond the patient. Conventional collimators are equipped with diaphragm devices of various types which are adjustable in order to vary the size of the X-ray beam. Due to recently enacted regulations, as well as general safety considerations, it is necessary for the X-ray beam to coincide exactly with the size of the film cassette toward which it is directed. Film cassettes having a standard size are most often used, although other sizes are available. However, the standard size cassette is used in both an upright and a transverse orientation so that the collimator diaphragm must therefore be frequently adjusted to vary the beam size in accordance with the cassette orientation.
At present, the collimator diaphragm is typically adjusted to bring the X-ray beam into conformity with the cassette by a manual procedure which utilizes a tracer light beam emitted from the collimator. A cassette is first inserted in a holding device and oriented as desired. After the cassette is positioned at the proper elevation, depending upon the height of the patient, the diaphragm controls are manually manipulated as the technician attempts to visually determine when the beam falls exactly on the four edges of the film cassette. Aside from the excessive time consumed by this tedious procedure, the present practice is unsatisfactory because of the error that invariably results, despite the care taken or the skill of the technician. Due to the nature of X-rays, the inaccurate correspondence in size or position of the beam with the cassette frequently leads to potentially dangerous situations.
It is therefore an important object of the present invention to provide an improved X-ray cassette holder for positioning a cassette in proper alignment with an incoming X-ray beam regardless of whether the longitudinal axis of the cassette is oriented either horizontally or vertically.
A further important object of the invention is to provide, in a cassette holder of the character described, means for conforming the dimensions and orientation of the X-ray beam to the dimensions and orientation of the film in the cassette. It is a significant feature of the invention that the collimator diaphragm is automatically adjusted to direct a beam having dimensions which correspond exactly to the dimensions of the film.
Another object of the invention is to provide a cassette holder of the character described that is easily and conveniently adjustable in vertical position.
Yet another object of the invention is to provide a means, associated with a cassette holder of the character described, for indicating the elevation of an inserted cassette to facilitate vertical alignment of the collimator therewith.
An additional object of the invention is to provide a cassette holder of the character described which includes means for preventing the emission of an X-ray beam unless the cassette is properly positioned with respect to the beam.
A still further object of the invention is to provide a cassette holder of the character described wherein the components are readily accessible for inspection, repair and replacement.
Other and further objects of the invention, together with the features of novelty appurtenant thereto, will appear in the course of the following description.